4 J.W. Doran, M.R. Zeiss Applied Soil Ecology 15 2000 3–11
desertification Oldeman, 1994. Indeed, degradation and loss of productive agricultural land is one of our
most pressing ecological concerns, rivaled only by human caused environmental problems like global
climate change, depletion of the protective ozone layer, and serious declines in biodiversity Lal, 1998.
Soil quality has been defined by the Soil Science Society of America Ad Hoc Committee on soil qual-
ity S-581 as ‘the capacity of a specific kind of soil to function, within natural or managed ecosystem bound-
aries, to sustain plant and animal productivity, main- tain or enhance water and air quality, and support hu-
man health and habitation’ Karlen et al., 1997. In discussion of the ambiguity of environmental terms
and the need to standardize their meanings, Johnson et al. 1997 defined soil quality as ‘a measure of the
condition of soil relative to the requirements of one or more biological species andor to any human purpose’.
The term ‘soil health’ is preferred by some for a discussion see Doran et al., 1996; Doran and Safley,
1997 because it portrays soil as a living, dynamic system whose functions are mediated by a diversity
of living organisms that require management and con- servation. Soil health, biodiversity, and soil resilience
are severely limited in extreme environments and are more sensitive to anthropogenic disturbance Freck-
man and Virginia, 1997. The terms soil quality and soil health will be used synonymously throughout this
paper. However use of the term soil quality will gen- erally be associated with a soils’ fitness for a specific
use and the term soil health used in a broader sense to indicate the capacity of soil to function as a vital liv-
ing system to sustain biological productivity, promote environmental quality, and maintain plant and animal
health. In this sense soil health is synonymous with sustainability. The quality of a soil includes an inher-
ent component, determined by the soil’s physical and chemical properties within the constraints set by cli-
mate and ecosystem. In addition, soil quality includes a component affected by management and land-use
decisions. Unfortunately, past management of agricul- ture and other ecosystems has substantially degraded
and reduced the quality of many soils throughout the world Saunders, 1992; Oldeman, 1994. In particular,
mechanical cultivation and the continuous production of row crops has resulted in physical loss of soil, dis-
placement through erosion, and large decreases in soil organic matter content with a concomitant release of
CO
2
to the atmosphere Houghton et al., 1983. Fur- ther, the projected doubling of the human population in
the next century threatens accelerated degradation of soils and other natural resources Power, 1996. Thus,
to preserve agriculture for future generations, we must develop production systems that conserve and enhance
soil quality.
As a small step towards this end, a conference entitled ‘Soil Health: Managing the Biological Com-
ponent of Soil Quality’ was held as part of the joint annual meeting of the Entomological Society
of America ESA and the American Phytopathol- ogy Society APS which convened in Las Vegas,
Nevada in November 1998. The goals of the con- ference were to increase awareness within the ESA
and APS of the utility of soil organisms as indica- tors of soil quality, and to permit researchers from
diverse disciplines to integrate results from multiple taxa of soil organisms. The overarching objective was
to help ‘translate science into practice’ by providing a forum for researchers and extension workers to
discuss farmer-participatory programs for managing soil quality. The papers published in this issue were
presented in abbreviated form during the conference.
2. Soil quality: indicator of sustainable land management
Developing sustainable land management systems is complicated by the need to consider their utility
to humans, their efficiency of resource use, and their ability to maintain a balance with the environment that
is favorable both to humans and most other species Harwood, 1990. In particular, we are challenged to
develop agricultural management systems that bal- ance the needs for production of food and fiber with
those for maintenance of the environment. More sim- ply stated by Tom Franzen, a midwestern farmer in the
USA, “a sustainable agriculture — sustains the peo- ple and preserves the land.” Soil quality is conceptu-
alized as the major linkage between the strategies for agricultural conservation management practices and
achievement of the major goals of sustainable agricul- ture Parr et al., 1992; Acton and Gregorich, 1995. In
short, the assessment of soil quality or health, and di- rection of change with time, is the primary indicator
of sustainable land management Karlen et al., 1997.
J.W. Doran, M.R. Zeiss Applied Soil Ecology 15 2000 3–11 5
Although soil’s contribution to plant productivity is widely recognized, soil condition also impacts water
and air quality. The quality of surface and sub-surface water has been jeopardized in many parts of the world
by intensive land management practices and the con- sequent imbalance of C, N, and water cycling in soil.
Agriculture is considered the most widespread con- tributor to nonpoint source water pollution in the USA
National Research Council, 1993. The major water contaminant in North America and Europe is nitrate
nitrogen, the principal sources of which are conver- sion of unmanaged land to intensive agriculture, an-
imal manures, atmospheric deposition, and commer- cial fertilizers. Human alterations of the nitrogen cy-
cle have almost doubled the rate of nitrogen input to terrestrial ecosystems over the past 30 years resulting
in large increases in the transfer of nitrogen from land to the atmosphere and to rivers, estuarines, and coastal
oceans Vitousek et al., 1997. Soil management prac- tices such as tillage, cropping patterns, and pesticide
and fertilizer use influence water quality. In addition, these management practices can influence atmospheric
quality through changes in the soil’s capacity to pro- duce or consume important atmospheric gases such
as carbon dioxide, nitrous oxide, and methane Rol- ston et al., 1993; Mosier, 1998. The present threat of
global climate change and ozone depletion, through elevated levels of greenhouse gases and altered hydro-
logical cycles, necessitates a better understanding of the influence of land management on soil processes
Bengtsson, 1998. In summary, the quality and health of soil determine agricultural sustainability Papen-
dick and Parr, 1992; Acton and Gregorich, 1995, en- vironmental quality Pierzynski et al., 1994, and as a
consequence of both, plant, animal, and human health Haberern, 1992; Harris et al., 1996.
Scientists make a significant contribution to sustain- able land management by translating scientific knowl-
edge and information on soil function into practical tools and approaches by which land managers can as-
sess the sustainability of their management practices Dumanski et al., 1992; Bouma, 1997. Specifically,
assessment of soil qualityhealth is needed to identify problem production areas, make realistic estimates of
food production, monitor changes in sustainability and environmental quality as related to agricultural man-
agement, and to assist government agencies in for- mulating and evaluating sustainable agricultural and
land-use policies Granatstein and Bezdicek, 1992. Use of one given approach for assessing or indexing
soil quality is fraught with complexity and precludes its practical or meaningful use by land managers or
policy makers Harris et al., 1996. However, the use of simple indicators of soil quality and health which
have meaning to farmers and other land managers will likely be the most fruitful means of linking science
with practice in assessing the sustainability of man- agement practices Romig et al., 1995, 1996.
3. Use of soil organisms as indicators of soil quality and health
